Brush motors include a stator, a rotor rotatably mounted to the stator and a brush assembly. The rotor includes a shaft, a commutator and a rotor core fixed to the shaft, and rotor windings wound around the rotor core and electrically connected with segments of the commutator. The brush assembly has brushes in sliding contact with the commutator to transfer electrical power there to.
When the motor operates, the rotor rotates relative to the stator so that the brushes and their power supply circuits are subject to voltage and current fluctuations as the brushes transfer from one segment of the commutator to the next, thus generating electromagnetic interference (EMI).
In order to suppress the motor EMI, filter capacitors and/or inductors are usually mounted on the brush assembly to prevent the motor from electrically interfering with objects outside the motor. However, because the motor usually has a small size, EMI generated at the brushes may be radiated to the motor terminals, known as the coupling effect, whereby EMI produced by the motor may still electrically interfere with the motor power supply circuit and objects outside the motor.
Thus there is a desire for a brush motor having improved EMI suppression.